ABSTRACT
Measurements of soil moisture changes, weight changes of a vegetated lysimeter or input-output differences of precipitation and evapotranspiration could define the balance, but, at present, these are largely inaccurate and available at only a few stations in Africa. Before this advance can be made for Africa there is need for experimental work to determine yield-potential evapotranspiration relationships for individual crops. Maps are at present being prepared for East Africa by the East Africa Agriculture and Forestry Research Organization. Since the scope of this study is so large, it was found that the solar radiation data published in the Quarterly Radiation Bulletins of the Union of South Africa Weather Bureau, supplemented by additional data collected in West Africa, were sufficient. Concurrent with this there must be continuing research into the individual components of the energy balance, notably evaporation, in the tropical lands of Africa.
